Liver disease caused by Hepatitis C Virus (HCV) infection is a major medical problem: no vaccine is available and therapy is only effective in a minority of patients. Virus-specific T cell responses are associated with clearance of HCV in acutely infected humans and chimpanzees. Based on these observations, the long term objective of the HCV vaccine program is to develop both prophylactic and therapeutic vaccines that elicit antiviral CD4+ and CD8+ responses capable of: i) reducing the rate of incidence and/or persistence of HCV infection following exposure (for prophylactic vaccine); ii) increasing the rate of clearance of HCV infection as a monotherapy, and/or in combination with current therapy or novel anti-viral therapy (for therapeutic vaccine). The present vaccine candidates are gene-based, encode for the 2000 amino acid-long HCV Non Structural region (NS3-NS5B) and utilize adenoviral vectors for delivery. These vectors have been shown to elicit potent CD4+ and CD8+ T cell responses in rodents and primates and protect chimpanzees from chronic infection. The Specific Aims of this Application are: 1) the production and characterization of cGMP lots of Adenovirus HCV vaccine vectors; 2) animal safety studies; 3) immunogenicity studies in nonhuman primates to determine dose and regimen. HCV is endemic in the world population: the most recent WHO estimate of the prevalence of HCV is 2%. Chronic infection leads to severe liver disease and cancer and is responsible for approximately 12,000 death cases/year in the U.S. This number is expected to increase drastically in the next 15-20 years due to the vast number of existing carriers, if effective new therapies are not soon discovered. Incidence rates are still significant (i.e. 30,000 new cases/year in the United States) and have remained constant over the last several years. Currently, treatment regimens for HCV infection are: inadequate due to poor efficacy and to poor tolerability, expensive and inaccessible to the majority of infected individuals on a worldwide basis. Therapeutic vaccination will provide for a new tool based on immunological mechanism to be used alone or in combination with current therapy or novel anti-viral drugs thereby increasing the probability of success to cure the disease. A significant epidemiologic impact on the spread of HCV infection will only occur subsequent to the development and introduction of an effective vaccine. [unreadable] [unreadable] [unreadable] [unreadable]